<?php
if ($file->type === 'php') {
    echo '<div class="content">';
    highlight_string($file->content);
    echo '</div>';
} elseif (in_array($file->type, array('txt', 'js', 'css'))) {
    echo '<div class="content">';
    echo nl2br($file->content);
    echo '</div>';
} else
    echo '<div class="error">Preview is not available for this file type.</div>';
?>